1. Field of the Invention
The present invention relates to coordinate input devices and, more particularly, to a coordinate input device having an input surface which is pushed to be operated.
2. Description of the Related Arts
Image input devices are known, wherein, for example, as a user touches (i.e., pushes) an input surface in the form of a flat plate with a pen or the like, the trace of the pen on the input surface is displayed on a monitor device as an image or stored in a memory device as image data. Such image input devices are used for games and drawing.
In order to detect an input position drawn on an input surface, a coordinate input device is used for detecting the input position, i.e., pushed position, is used as the input surface.
For example, a coordinate input device is configured as shown in FIG. 1. In FIG. 1, an input detecting member 1 has a resistive surface RY1 in the form of a rectangle and electrodes 1a and 1b formed on both side portions of the resistive surface constituting the longer sides of the rectangle. An input detecting member 2 also has a resistive surface RX1 in the form of a rectangle and electrodes 2a and 2b formed on both side portions of the resistive surfaces constituting the shorter sides of the rectangle.
A voltage of, for example, 5 V is applied to the electrode 1b through a switch S.sub.3. The electrode 1a is grounded through an external resistor Rg and a switch S.sub.4.
A voltage of, for example, 5 V is applied to the electrode 2b through a switch S.sub.5. The electrode 2a is grounded through a switch S.sub.6.
The electrode 1b is connected to a terminal T.sub.x of a switch S.sub.7 while the electrode 2b is connected to a T.sub.y of the switch S.sub.7.
A resistive portion RS1 is connected to the electrode 1b of the input detecting portion 1, the resistive portion RS1 being on the same plane as the resistive surface RY1 but on the reverse side of the plane. An electrode 1c is provided on the other end of the resistive portion RS1.
This electrode 1c is grounded through a switch S.sub.20. The switches S.sub.3, S.sub.4, S.sub.5, S.sub.6, S.sub.7 and S.sub.20 are constituted by semiconductor switches.
Lead wires 21 and 22 are connected to different positions of the resistive portion RS1 provided between the electrodes 1b and 1c. The lead wire 21 is connected to conductors ay, by, cy, dy and ey for face-plate switches. The lead wire 22 is connected to conductors fy, gy, hy, iy and jy for face-plate switches.
Lead wires 23, 24, 25, 26 and 27 are connected to different positions of the resistive surface RX1 of the input detecting member 2. The lead wire 23 is connected to face-plate switch conductors ax and fx. The lead wire 24 is connected to face-plate switch conductors bx and gx. The lead wire 25 is connected to face-plate switch conductors cx and hx. The lead wire 26 is connected to face-plate switch conductors dx and ix. The lead wire 27 is connected to face-plate switch conductors ex and jx.
8 designates an analog-to-digital converter for converting a voltage supplied from the switch S.sub.7 into digital data, and 9 designates an image memory portion for storing the digital data output by the A-D converter 8 as an input coordinate value. 10 designates a controller for controlling the operation of the image memory portion 9 and the switching of the switches S.sub.3, S.sub.4, S.sub.5, S.sub.6, S.sub.7 and S.sub.20.
In this coordinate input device, the input detecting member 1 and 2 are overlapped in a face-to-face relationship with a spacer SP interposed therebetween as shown in FIG. 2 so that the resistive surfaces RX1 and RY1 will not be in contact with each other. The side of a surface sheet 11 is used as an input surface, and an image input device 12 as shown in FIG. 3 is configured using such a coordinate input device.
In the image input device 12, the area 13 indicated by the oblique lines represents the input surface formed by the input detecting members 1 and 2. When a pen P is moved on this input surface 13, the coordinates of each of pushed points are detected by the coordinate input device in FIG. 1 and are stored in the image memory 9. Although not described in detail, by supplying the data stored in this image memory 9 to a monitor device 14 as a picture signal, an image which is the same as the trace drawn on the input surface 13 by the pen P is output as a monitor image.
In this coordinate input device, when a point is pushed with the pen P as shown in FIG. 2, the resistive surfaces RY1 and RX1 electrically contact each other only at the pushed area. The X- and Y-coordinates of the point on the input surface can be obtained by detecting the resistance produced at that time.
As shown in FIG. 3, a face-plate switch portion 30 is provided in a position different from that of the input surface 13, and input switches are provided as indicated by a through j.
The input switches a through j are formed by face-plate switch conductors ay-jy and ax-jx.
As shown in FIG. 4(a), the face-plate switch conductors ay-ey are formed by a conductor, e.g., silver paste, which is continuous with the lead wire 21 while the face-plate switch conductors fy-jy are formed as a conductor which is continuous with the lead wire 22.
As shown in FIG. 4(b), pairs of the face-plate switch conductors ax and fx, bx and gx, cx and hx, dx and ix, and ex and jx are formed of, e.g., silver paste, as conductors which are continuous with the lead wires 23, 24, 25, 26 and 27. Spacers SP are provided on the face-plate switch conductors ax-jx at predetermined intervals.
As typically illustrated in FIG. 1, pairs of the face-plate switch conductors ax and ay, bx and by, cx and cy . . . , jx and jy are each overlapped.
Referring to FIG. 4(c) wherein the face-plate switch conductors ax and ay are shown as an example, the face-plate switch conductors ax and ay are kept away from each other by a spacer SP to form an input switch a.
When the input switch a is pushed by the pen P or the like, the face-plate switch conductors ax and ay contact each other at the pushed position. Detection of the contact between the face-plate switch conductors ax and ay provides detection of the input operation on the input switch a. Input operations on the input switches b-j are similarly detected.
A description will now be made on operations of detecting X- and Y-coordinate values input from the input surface 13 and detecting the input of the input switches a-j in this coordinate input device.
To detect X- and Y-coordinate values input from the input surface 13 and the input of the input switches a-j, the controller in FIG. 1 supplies switch control signals S.sub.sw to the switches S.sub.3, S.sub.4, S.sub.5, S.sub.6, S.sub.7 and S.sub.20 to enable sequential switching of three kinds of operation modes.
Specifically, the three kinds of operation modes are (1) an X-coordinate detection mode in response to input operations on the input surface 13 or the face-plate switch portion 30, (2) a Y-coordinate detection mode in response to input operations on the face-plate switch portion 30 and (3) a Y-coordinate detection mode in response to input operations on the input surface 13.
The modes (1), (2) and (3) are switched, for example, in a cycle of 1 KHz to allow input from the input surface 13 and the face-plate switch portion 30 to be always responded.
In the X-coordinate detection mode in response to an input operation on the input surface 13 or face-plate switch portion 30, the switches are controlled as follows.
Switch S.sub.3 : Off PA0 Switch S.sub.4 : Off PA0 Switch S.sub.5 : On PA0 Switch S.sub.6 : On PA0 Switch S.sub.7 : Connected to T.sub.x PA0 Switch S.sub.20 : Off PA0 Switch S.sub.3 : On PA0 Switch S.sub.4 : Off PA0 Switch S.sub.5 : Off PA0 Switch S.sub.6 : Off PA0 Switch S.sub.7 : Connected to T.sub.y PA0 Switch S.sub.20 : On PA0 Switch S.sub.3 : On PA0 Switch S.sub.4 : On PA0 Switch S.sub.5 : Off PA0 Switch S.sub.6 : Off PA0 Switch S.sub.7 : Connected to T.sub.y PA0 Switch S.sub.20 : Off
As a result, a voltage of +5 V is applied to the electrode 2b of the input detecting member 2, and the electrode 2a is grounded. Therefore, the voltage on the resistive surface RX1 varies in the direction of the X-axis. For example, in an ideal state, the voltage is 5 V at the area where the surface is in contact with the electrode 2b, 0 V at the area where it is in contact with the electrode 2a, and 2.5 V at the center in the direction of the X-axis thereof.
On the other hand, the electrode 1b acts as a terminal for detecting X-coordinate values for the input detecting member 1. Specifically, the output voltage of the electrode 1b is supplied to the A-D converter 8 through the terminal T.sub.x of the switch S.sub.7.
When the resistive surfaces RX1 and RY1 contact each other at a point of the input surface 13 as a result of a push on that point in the state as described above, the voltage of the resistive surface RX1 corresponding to the pushed point, i.e., a voltage as the value of the X-coordinate value, is obtained. This voltage is converted into digital data by the A-D converter 8 and is fetched into the image memory portion 9 as an X-coordinate value.
In this mode, the voltage at the connection between the resistive surface RX1 and the lead wire 23 is applied to the face-plate switch conductors ax and fx. Further, the voltage at the connection between the resistive surface RX1 and the lead wire 24 is applied to the face-plate switch conductors bx and gx; the voltage at the connection between the resistive surface RX1 and the lead wire 25 is applied to the face-plate switch conductors cx and hx; the voltage at the connection between the resistive surface RX1 and the lead wire 26 is applied to the face-plate switch conductors dx and ix; and the voltage at the connection between the resistive surface RX1 and the lead wire 27 is applied to the face-plate switch conductors ex and jx.
Therefore, when any of the input switches a-j of the face-plate switch portion 30 is pushed, the two upper and lower face-plate switch conductors (*x and *y) constituting that input switch contact each other. As a result, the voltage at the connection between the resistive surface RX1 and any one of the lead wires 23-27 (i.e., a voltage as an X-coordinate value) appears at the electrode 1b through the lead wire 21 or 23 and the resistive portion RS.
For example, if the input switch e has been pushed, a voltage corresponding to the position on the resistive surface RX1 to which the lead wire 27 is connected is obtained at the electrode 1b.
This voltage is converted into digital data by the A-D converter 8 and is fetched into the image memory portion 9 as an X-coordinate value.
Thus, referring to the face-plate switch portion 30, it is possible to judge an input switch which has been pushed to be any of "a or f", "b or g", "c or h", "d or i", and "e or j" according to the coordinate value detected in this mode.
As described above, the X-coordinate value for a push on either the input surface 13 or the face-plate switch portion 30 is first detected in the mode (1).
It should be noted that it is not possible at this stage to judge whether the detected X-coordinate value is a result of a push on the input surface 13 or a push on the face-plate switch portion 30.
In the Y-coordinate detection mode in response to an input operation on the face-plate switch portion 30, the switches are controlled as follows.
In this case, a voltage of +5 V is applied to the electrode 1b of the input detecting member 1, and the electrode 1c is grounded. Since the electrode 1a is not grounded at this time, a voltage of +5 V is applied to the resistive portion RS1. Therefore, the voltage at the resistive portion RS1 varies in the direction of the Y-axis. In other words, the connections to the lead wires 21 and 22 have different voltages.
At this time, the electrode 2b acts as a terminal for detecting Y-coordinates for the input detecting member 2. Specifically, the output voltage of the electrode 2b is supplied to the A-D converter 8 through the terminal T.sub.y of the switch S.sub.7.
In this state, no Y-coordinate value is obtained for a push on the input surface 13. In other words, the resistive surface RY1 has no resistance distribution as a result of the application of a voltage.
On the other hand, in this mode, the voltage at the connection between the resistive portion RS1 and the lead wire 21 is applied to the face-plate switch conductors ay, by, cy, dy and ey. Further, the voltage at the connection between the resistive portion RS1 and the lead wire 22 is applied to the face-plate switch conductors fy, gy, hy, iy and jy.
Therefore, when any of the input switches a-j of the face-plate switch portion 30 is pushed to cause the two upper and lower face-plate switch conductors (*x and *y) constituting that input switch to contact each other, the voltage at the connection between the resistive portion RS1 and the lead wire 21 or 22 is obtained at the electrode 2b of the input detecting member 2.
This voltage is converted into digital data by the A-D converter 8 and is fetched into the image memory portion 9 as a Y-coordinate value. This Y-coordinate value is a coordinate value which is related to an operation on the face-plate switch portion 30 and from which an input switch which has been pushed can be judged to be "any of a-e" or "any of f-j".
The fact that a Y-coordinate value can be obtained in this mode (2) supports a judgement that the X-coordinate value obtained in the mode (1) was a coordinate value related to an operation on the face-plate switch portion 30, and it is possible to know which of the input switches a-j has been pushed from the combination of the X- and Y-coordinate values.
In the Y-coordinate detection mode in response to an input operation on the input surface 13, the switches are controlled as follows.
In this case, a voltage of +5 V is applied to the electrode 1b of the input detecting member 1, and the electrode 1a is grounded through the external resistor Rg. Since the electrode 1c is not grounded at this time, a voltage of +5 V is applied to the resistive surface RY1. Therefore, the voltage on the resistive surface RY1 varies in the direction of the Y-axis.
In this state, no Y-coordinate value is obtained for a push on the face-plate switch portion 30. In other words, the resistive portion RS1 has no resistance distribution as a result of the application of a voltage.
At this time, the electrode 2b acts as a terminal for detecting Y-coordinates for the input detecting member 2 like in the mode (2). Specifically, the output voltage of the electrode 2b is supplied to the A-D converter 8 through the terminal T.sub.y of the switch S.sub.7.
In this state, a voltage on the resistive surface RY1 corresponding to the pushed point on the input surface 13, i.e., a voltage as a Y-coordinate value, is obtained at the electrode 2b. This voltage is converted into digital data by the A-D converter 8 and is fetched into the image memory portion 9 as a Y-coordinate value.
The fact that a Y-coordinate value can be obtained in this mode (3) supports a judgement that the X-coordinate value obtained in the mode (1) was a coordinate value related to an operation on the input surface 13, and the pushed position on the input surface 13 is fetched as the X- and Y-coordinate values.
Such a configuration of the coordinate input device makes it possible to input images etc. and to use the face-plate switch portion 30 as function switches etc. of various types.
FIG. 5 shows another example of the configuration of the coordinate input device. Parts identical to those in the configuration in FIG. 3 are given like reference numbers and will not be described to avoid duplication.
In this case, input detecting members 15 and 16 are provided as the input detecting members. The input detecting member 15 has a resistor RY2 formed along a shorter side (in the direction of the Y-axis) of an input surface in the form of a rectangle. Electrodes 15a and 15b are provided on both ends of the resistor RY2, and lead wires 15e are led out from the resistor RY2 in parallel with the X-axis thereof. The lead wires 15e are formed at intervals corresponding to pixels in the direction of the Y-axis.
The input detecting member 16 has a resistor RX2 formed along a longer side (in the direction of the X-axis) of the input surface in the form of a rectangle. Electrodes 16a and 16b are provided on both ends of the resistor RX2, and lead wires 16e are led out from the resistor RX2 in parallel with the Y-axis thereof. The lead wires 16e are formed at intervals corresponding to pixels in the direction of the X-axis.
In addition, a resistive portion RS2 is connected to the electrode 15b of the input detecting member 15 on the same plane as the resistor RY2 but on the reverse side of the plane. An electrode 15c is provided on the other end of the resistive portion RS2.
This electrode 15c is grounded through the switch S.sub.20.
Lead wires 21 and 22 are connected to different positions of the resistive portion RS2 provided between the electrodes 15b and 15c. The lead wire 21 is connected to face-plate switch conductors ay, by, cy, dy and ey. The lead wire 22 is connected to face-plate switch conductors fy, gy, by, iy and jy.
Lead wires 23, 24, 25, 26 and 27 are connected to different positions of the resistor RX2 of the input detecting member 2. The lead wire 23 is connected to face-plate switch conductors ax and fx. The lead wire 24 is connected to face-plate switch conductors bx and gx. The lead wire 25 is connected to face-plate switch conductors cx and hx. The lead wire 26 is connected to face-plate switch conductors dx and ix. The lead wire 27 is connected to face-plate switch conductors ex and jx.
The coordinate detecting method used here is substantially the same as that in the example in FIG. 1. Specifically, when a point on the input surface 13 is pushed, one of the lead wires 15e and one of the lead wires 16e contact each other. When the switches S.sub.3, S.sub.4, S.sub.5, S.sub.6, S.sub.7 and S.sub.20 are in the mode (1), a certain voltage on the resistor RX2 corresponding to the direction of the X-axis is obtained at the electrode 15b. When the switches are in the mode (3), a certain voltage on the resistor RY2 corresponding to the direction of the Y-axis is obtained at the electrode 16b. These voltages are fetched into the image memory portion 9 as coordinate data.
When a certain input switch of the face-plate switch portion 30 is pushed, the upper and lower face-plate switch conductors contact. When the switches S.sub.3, S.sub.4, S.sub.5, S.sub.6, S.sub.7 and S.sub.20 are in the mode (1), a voltage on the resistor RX2 corresponding to the connecting position of any one of the lead wires 23-27 is obtained at the electrode 15b. When the switches are in the mode (2), a voltage on the resistive portion RS corresponding to the connecting position of the lead wire 21 or 22 is obtained at the electrode 16b. As a result, it is judged which of the input switches a-j has been operated.
In such a coordinate input device, the X-Y coordinate detecting area on the input surface 13 is generally set in the form of a rectangle to comply with, for example, the monitor screen 14 of the image input device as shown in FIG. 3. In other words, the lengths of the X- and X-axes are different from each other.
Since the X- and Y-axes as the coordinate axes are different, the numbers of pixels assigned to the X- and Y-directions are different on the memory for storing detected coordinate data.
However, if the same voltage is applied to the X-axis resistor RX2 and the Y-axis resistor RY2 and voltages obtained for coordinates on the X- and Y-axes are converted into digital data using the same A-D converter 8, the coordinate data obtained from the A-D converter 8 will not be compatible with the memory pixel assigned to the coordinate in the image memory portion 9.
For example, assume that the ratio between the sizes of the X- and Y-coordinates and the ratio between the numbers of pixels assigned to the X- and Y-coordinates are both 256:212; the same voltage of 5 V is applied to both of the resistors RX2 and RY2 for detection along X- and Y-axes, respectively; and data conversion is performed using an A-D converter 8 having resolution of 256. In this case, detection of an X-coordinate can be performed without problem because a voltage corresponding to an input position in the direction of the X-axis is processed by the A-D converter 8 of resolution of 256 and is stored in a memory having 256 memory pixels in the image memory portion 9.
However, to detect a Y-coordinate, a voltage corresponding to an input position in the direction of the Y-axis must be converted by the A-D converter 8 of resolution of 256 into data in 212 steps corresponding to memory pixels. It is of course very difficult to do this, and the Y-coordinate data can not be properly processed in the image memory portion 9.
In order to solve this problem, for example, the external resistor Rg is connected to the Y-axis (the direction of the shorter sides) in series through the electrode 1a as shown in FIG. 1. The value of the external resistor Rg is chosen so that the voltage (excluding the voltage applied to the external resistor Rg) applied to the resistor RY2 of the Y-axis input coordinate surface will be equal to the ratio of the length of the Y-axis to the length of the X-axis. Specifically, in the example wherein X:Y=256:212, a relationship that RY2:Rg=212:44 is to be satisfied. Thus, the voltage detected on the resistor RY2 is adapted to the resolution of 256 to solve the above-described problem.
The adjustment using the external resistor Rg is also employed in the example of configuration in shown in FIG. 1 to solve the problem associated with the ratio between the X and Y pixels.
However, in general, the resistance of the resistive flat plates for detecting coordinates, i.e., the resistive surfaces RX1 and RX2 for the X-axis plane and the resistive surfaces RY1 and RY2 for the Y-axis plane is not so accurately controlled.
Although the resistance of the resistive surfaces per unit area can be made substantially uniform by forming the resistive surfaces by printing, the resistance of completed input detecting members as a whole varies from member to member within the range of about .+-.20%.
Therefore, the external resistor Rg must be a variable resistor and, in order to solve the problem associated with the ratio between the X- and Y-pixels, the resistance of the external resistor Rg must be adjusted for each coordinate input device during manufacture so that RY1 (and RY2): Rg will be adjusted to the above described ratio (or an integral multiple thereof).
In other words, the above-described coordinate input device has had a problem in that the addition of the external resistor Rg increases the number of parts and the cost of the device and in that the adjustment of the resistance of the external resistor Rg reduces processing efficiency.
Further, when it is attempted to perform detection not only on the input surface 13 but also on input on the face-plate switch portion 30 as described above, it is necessary to provide the resistive portion RS, electrode 1c (or 15c) and switch 20. Especially, wiring is required at three positions on the input detecting member to accommodate the electrodes 1a, 1b and 1c, which has resulted in a problem in that the circuit configuration and the routing of the printed wires become complicated.
In addition, the fact that one coordinate detecting operation involves three modes of operation as described above has resulted in an increase in the time required for the detecting operation.